1. Field of the Invention
With reference to the classification of art as established in the United States Patent and Trademark Office the present invention is found in the general Class of art entitled, "Measuring and Testing" (Class 73) and more particularly in the subclass entitled, "thermometer-indicating tube-type" (subclass 371).
2. Description of the Prior Art
Thermometers are well known and particularly the clinical thermometer which is constructed of glass with a capillary tube and which uses mercury. This thermometer, of course, is quite expensive and is not a throw-away thermometer. Many attempts to make inexpensive thermometers have been made and in these thermometers the use of non-metallic fluid has been particularly stressed. In many cases the indicating material is a solid until it reaches approximately 90.degree. Fahrenheit at which point it becomes liquid and is moved into a groove formed in a part of the thermometer. Particularly shown with such a device is U.S. Pat. No. 3,688,582 issued Sept. 5, 1972 to GRADISHAR. Another thermometer of this type is seen in U.S. Pat. No. 3,469,451 issued to EIZENBERG on Sept. 30, 1969. Another patent pertaining to the disposable thermometer concept is seen in U.S. Pat. No. 3,487,693 to WEINSTEIN which issued Jan. 6, 1970. Also of note are U.S. Pat. No. 3,745,831 which issued on July 17, 1973 to ROTHSTEIN; U.S. Pat. No. 3,631,721 which issued Jan. 2, 1969 to NOLLEN and U.S. Pat. No. 3,872,729 which issued Mar. 25, 1975 to AYRES. In these and other patents found in the prior art the forming of a capillary tube has been both expensive and lacking in the required accuracy and the resulting product has been less than satisfactory.
A conventional thermometer which is constructed of glass and has a restriction in the capillary tubing is very expensive. When in use over a period of time by several different patients or for several different contagious diseases a thermometer which is unsatisfactorily or improperly cleaned and sterilized provides insufficient protection against transmitting germs from one patient to another in hospital use. In addition to the infection hazard, a broken thermometer and the ingestion of mercury and glass is very undesirable and hazardous. Since the sterilization and the cost of a clinical thermometer constructed of glass and using mercury is expensive, a disposable thermometer costing less than ten cents each to the hospital is both desirable and a time saving convenience unit.